Method for the preparation of carboxylic acids by an oxidizing decomposition of organic compounds containing longer carbon chains

ABSTRACT

Carboxylic acids can be prepared by an oxidizing decomposition of organic compounds having longer carbon chains. The organic compounds are treated with potassium permanganate in acetic acid as solvent, resulting in the long carbon chains being split up to form carboxylic acids having shorter carbon chains.

United States Patent [191 Dinh-Nguyen et al. 1 Feb. 20, 1973 METHOD FORTHE PREPARATION OF [56] References Cited CARBOXYLIC ACIDS BY AN UNITEDSTATES PATENTS OXIDIZING DECOMPOSITION OF 3,196,182 7/1965 Cox ..260/533X ORGANIC COMPOUNDS CONTAINING 3,646,078 2/1972 Fanning". LONGER CARBONCHAINS 2,674,613 4 1954 Nelson [7 1 Inventors: g y g y Aino Raal2,721,149 10/1955 Nelson ..260/4l3 X both of Molndal, Sweden OTHERPUBLICATIONS [73] Assignee: Incentive Research & Development Bar k t etaL, mum, Chem, Soc, 1956, p.

Aktiebolag, Bromma, Sweden 4685-4687,

[22] Flled: 1969 Primary Examiner-Lewis Gotts [21] Appl. No.: 883,642Assistant Examiner-Ethel G. Love Att0rneyBrumbaugh, Graves, Donohue and[30] Foreign Application Priority Data Raymond Dec. 11, 1968 Sweden..l6972/68 [57] ABSTRACT Carboxylic acids can be prepared by anoxidizing [52] Cl 260/413 260/ decomposition of organic compounds havinglonger 51 I t Cl C68]! 17/36 carbon chains. The organic compounds aretreated 5 81 11 with potassium permanganate in acetic acid as Solvent,

Field of Search ..260/4l3, 533 R resulting in the long carbon chainsbeing split up to form carboxylic acids having shorter carbon chains.

5 Claims, No Drawings METHOD FOR THE PREPARATION OF CARBOXYLIC ACIDS BYAN OXIDIZING DECOMPOSITION OF ORGANIC COMPOUNDS CONTAINING LONGER CARBONCHAINS The invention is concerned with a method for the preparation ofcarboxylic acids by an oxidizing decomposition of organic compoundscontaining longer carbon chains, particularly organic compounds havinglonger, saturated, non-branched carbon chains.

It is known from the field of analysis that it is possible to determinethe position of the double bonds in an unsaturated carbon chain by anoxidizing decomposition of the carbon chain by means of potassiumpermanganate, and asubsequent identification of the carboxylic acidsthus formed. The reaction maybe described in this way:

This reaction can be performed in acetone at normal temperature. It isalso known that methylated fatty acids can be decomposed by being boiledin acetone for several days. The carbon chain is split up at the placeof branching, and the corresponding methyl ketone is formed.

In these known methods the carbon chain is split up at defined places,viz. at the double bonds or at the places of branching. It has now beenfound, according to the present invention, that it is possible to obtainan oxidizing decomposition of a saturated, non-branched carbon chain soas to form homologous monocarboxylic and dicarboxylic acids by oxidizingthe carbon chain by means of potassium permanganate in acetic acid assolvent, the acetic acid being entirely or nearly free from water. Thetemperature should preferably be higher than 70 C. and up to the boilingpoint of the solution at normal pressure.

Alternatively, manganese dioxide and sulphuric acid that the reactionproduct 'c'drit'aihKar'bi 'li acid methyl esters of various carbon chainlengths. Selected reaction conditions produces a reaction mixture inwhich carbon chains containing eight carbon atoms are prevailing. It ispossible to control, to some extent, the carbon chain length in thefinal product, by varying the reaction conditions. A shorter reactiontime displaces the prevailing carbon chain length towards longer chains.In the oxidizing decomposition of methyl stearate a reduction of thereaction time has resulted, i.a., in the formation of keto acidscontaining 18 carbon atoms in the carbon chain and having the oxo groupsituated in the position C6 to C10 or C15 to C17.

Examples of substances which can advantageously be subjected to theoxidizing decomposition of the invention are hexadecanoic acid(palmitinic acid), octadecanoic acid (stearic acid), methyloctadecanoate (stearic acid methyl ester), tripalmitin, beeswax,ntetradecanol- 1 hexadecane, docosane, 2,6,10,15,19,23-hexamethyltetracosane (squalan), and paraffin wax (melting point 6872 C). Thetable below gives the reaction conditions, the qualitative compositionof the fatty acid components of the final product, and the percentage ofmaterial which has not been decomposed after a certain time at thetemperature stated.

The oxidizing decomposition in acetic acid at an inhaving an industrialuse, such as adipic acid (C6),

pimelic acid (C7), suberic acid (C8), and sebacic acid (C 10).

Reaction conditions Reaction products Ratio Non-destarting Monocar-Dicarcomposed Time, Temp., material boxylic boxylic material Startingmaterial hours C. to KMnO acids acids percent Fatty acids {Hexadecanoicacid... 6 76-78 1:5 C6C15 04-014 32. 4

Octadecanoic acid-.. 48 80 1:5

. 1 80 1:5 2 80 1:5 3 80 1:5 Esters Methyloctadecanoate 4 80 1:5 6 801:5 48 80 1:5 18 80 1:3 Glycerides 'Iripalmitin 24 115 1:5 Waxes Beeswax24 115-120 1:5 Alcohols Tetradecanol1 l8 115-120 1:5

24 115-120 Hexadccana 26 115-120 1 :5 Hydrocarhons Docosane 24 116 1:52, 6, 10, 15, 1!), 2'1 lrcxnmcthyltctracosunc.. 12 115-120 1:5 Parallinwax (M.I. (38-72 C.) 24 116420 1:5 C5-C24 C5C18 MnOri-llzSOa can be usedas oxidizing agent in lieu of potassium permanganate.

The reaction of the invention is non-specific, because it appears thatthe carbon chain is split up at random at any place of the chain,resulting in the formation of the entire homologous series ofmonocarboxylic and dicarboxylic acids, from acids having a chain lengthof a couple of carbon atoms to acids having the same carbon chain lengthas the starting material. This can be illustrated by subjecting methylstearate to the oxidizing decomposition of the invention. An analysis ofthe reaction product in a gas chromatograph reveals The method of theinvention is of a particular interest in the preparation of deuteratedorganic com pounds. it is known from British Pat. No. 1,103,607 that itis possible to replace the hydrogen of organic compounds completely bydeuterium by reacting the organic compounds with heavy water in alkalineconditions by means of a platinum catalyst and in the presence of apromoter consisting of deuterium peroxide. The deuteration process inexpensive, and it is therefore desired to. deuterate a long chaincompound, and subsequently to split up said deuterated compound to formvarious deuterated compounds containing shorter carbon chains, insteadof deuterating short chain compounds separately. It has not beenpossible to achieve said desire by splitting the deuterated long chaincompounds by the known processes referred to above. This is due to thefact that the reaction solution has received hydroxyl ions:

The presence of hydroxyl ions results in a hydrogen deuterium exchangein the deuterated organic molecules. Consequently, the deuteratedcompounds suffer a partial loss of their deuterium content. In thereaction of the invention, acetic acid being used as solvent, thereaction solution will have no content of hydroxyl ions, and thedeuterated carbon chains do not, therefore, loose any deuterium in thesplitting operation. The preparation of deuterated carboxylic acidsaccording to the present invention comprises deuterating ahydrogen-containing organic compound having a comparatively long carbonchain, preferably a carbon chain of at least 12 carbon atoms, withdeuterium oxide in the presence of an alkaline, a deuteroxide, a metalcatalyst of the platinum group, and a deuterium peroxide promoter, andtreating the deuterated compound thus prepared with potassiumpermanganate and sulphuric acid in acetic acid as solvent, at atemperature of at least 70 C. A preferred process for the preparation ofdeuterated carboxylic acids comprises deuterating a deuteratable organiccompound containing hydrogen, said organic compound having acomparatively long carbon chain, preferably a carbon chain of at least12 carbon atoms, said deuterating operation involving replacing hydrogenwith deuterium by reacting said organic compound with heavy water, as adeuterium source, with the aid of sodium deuteroxide and reduced Adamscatalyst (PtO, H O), in the presence of a promoter consisting ofdeuterium peroxide, and exposing the comparatively long-chaineddeuterated organic compound, thus prepared, to an oxidizingdecomposition by treating it with potassium permanganate and sulphuricacid in acetic acid as solvent, at a temperature of at least 70 C., fora time sufficient to split up the comparatively long carbon chain of theV deuterated organic compound into shorter chains.

EXAMPLE 1: OXIDIZING DECOMPOSITION OF N- 0.100 g docosane (0.323 mole)was placed in a reaction tube, the upper, narrower portion of whichcould be cooled by means of a cooling means. 2 ml acetic acid, having apurity of 99 100 percent, and 0.5 g pulverized potassium permanganate(3.16 10' mole) was added. The reaction tube was placed in an oil bath,controlled by a thermostat, and was allowed to remain there for- 24hours at 115 C. 20 percent docosane did, not react. The oxidationproducts were prepared for a gas chromatographic analysis in this way.

The excess of potassium permanganate ions was reduced by a saturatedsolution of sodium hydrogen sulfite in water. The mixture was extractedquantitatively with diethyl ether. The ether extracted was separatedfrom the underlying phase. The solvent was evaporated, and the residuewas esterified with methanol. When calculating the excess of methanol,the acetic acid having been extracted into the ether phase has to betaken into consideration. The methyl esters were analyzed in a gaschromatograph.

EXAMPLE 2: OXIDIZING DECOMPOSITION OF N- METHYL OCTADECANOATE (METHYLSTEARATE, CH (CI-I,), COOCI-I 5 g methyl octadecanoate (16.75 10"mole)were placed in a flask having three necks. The flask was placed in awater bath, controlled by a thermostat, and was provided with a cooler,a thermometer, and a magnetic stirrer. The temperature of the water bathwas set at C. ml concentrated acetic acid, having a purity of 98-100percent, was added to dissolve the stearate. 15 g potassium permanganate(95.10' mole) was added during a period of 10 minutes. The reactionstarted when approximately half the quantity of permanganate had beenadded. Samples are taken, first each half hour, later with longerintervals. The samples were prepared for a gas chromatographic analysisas.

has been described in Example 1. 23.5 percent nondecomposed stearateremains after 18 hours at 80 C. The reaction mixture was allowed tostand, while being stirred, for another 3 hours at 1 15 C., resulting in22.6 22.6 percent methyl octadecanoate being non-decomposed.

EXAMPLE 3: OXIDIZING DECOMPOSITION OF N- I-IEXADECANOIC ACID (palmiticacid), CH (CH CODE.

20 g hexadecanoic acid (78-10' mole) was dissolved in a flask in 400 ml98 percent acetic acid, and was heated to 70 C. in a water bath,controlled by a thermostat. The flask was provided with a magneticstirrer and a reflux cooler. 100 g pulverized potassium permanganate(633.10" mole) was added in small quantities during a period of 3 hours,and the temperature was simultaneously increased slowly to 78 C. Themixture was allowed to react for 6 hours, while being stirred, and theheating was now switched off overnight. A sample of 1 ml was taken thenext day, and was prepared for a gas chromatograph analysis as describedin Example 1. The reaction mixture contained 32.4 percent non-decomposedstarting material.

EXAMPLE 4. OXIDIZING DECOMPOSITION OF N TETRADECANOLE, CH (CI-I ofconcentrated sulfuric acid was added. The reaction tube was allowed tostand in an oil bath for 24 hours at 1 1 5 C.

The reaction product was treated as described in Example 1, includingthe esterifying operation. It was What is claimed is:

l. A method for the preparation of carboxylic acids by an oxidizingdecomposition of organic compounds containing long carbon chains andselected from the group consisting of fatty acids esters, glycerides,waxes, alcohols and hydrocarbons, comprising treating said compoundswith potassium permanganate or with manganese dioxide and sulfuric acid,in an acetic acid solvent.

2. A method according to claim 1 wherein the decomposition is carriedout at a temperature of between 70 C. and the boiling point of thesolution at normal pressure, and wherein the acetic acid solvent iswater-free.

3. A method for the preparation of deuterated carboxylic acids by anoxidizing decomposition of deuterated organic compounds having a longcarbon chain, and selected from the group consisting of fatty acids,

esters, glycerides, waxes, alcohols and hydrocarbons, comprisingtreating said compounds with potassium permanganate or with manganesedioxide and sulfuric acid in a water-free acetic acid solvent.

4. A method according to claim 3 wherein the deuterated organiccompounds have a carbon chain of at least 12 carbon atoms.

5. A method for the preparation of deuterated carboxylic acidscomprising exposing a long chain deuterated organic compound selectedfrom the group consisting of fatty acids, ester, glycerides, waxes,alcohols and hydrocarbons to an oxidizing decomposition by treating itwith potassium permanganate and sulfuric acid in a water-free aceticacid solvent, at a temperature of at least C. and for a period of timesufficient to split up the long carbon chain of the deuterated organiccompound into shorter chains.

mg? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,717,664 Dated February 20,1973

Inventofls) NGUYEN DINH-NGUYEN and AINO RAAL It is certified that errorappears in the. above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 5, line 8, after "acid" insert -as the oxidizing agent--;

Column 6, line 4, after "acid" (first occurrence) insert as theoxidizing agent,-;

Column 6, line 13, after "permanganate" insert or withmanganesedioxide-;

Column 6, line 14, after "acid" (first occurrence) insert astheoxidizing agent- Signed and sealed this 9th day of April 197L (SEAL)Attest:

EDWARD PLFIETCILER,JR. 'MRSHALL DAM:

Attesting Officer oommissioner of Patents

1. A method for the preparation of carboxylic acids by an oxidizingdecomposition of organic compounds containing long carbon chains andselected from the group consisting of fatty acids esters, glycerides,waxes, alcohols and hydrocarbons, comprising treating said compoundswith potassium permanganate or with manganese dioxide and sulfuric acid,in an acetic acid solvent.
 2. A method according to claim 1 wherein thedecomposition is carried out at a temperature of between 70* C. and theboiling point of the solution at normal pressure, and wherein the aceticacid solvent is water-free.
 3. A method for the preparation ofdeuterated carboxylic acids by an oxidizing decomposition of deuteratedorganic compounds having a long carbon chain, and selected from thegroup consisting of fatty acids, esters, glycerides, waxes, alcohols andhydrocarbons, comprising treating said compounds with potassiumpermanganate or with manganese dioxide and sulfuric acid in a water-freeacetic acid solvent.
 4. A method according to claim 3 wherein thedeuterated organic compounds have a carbon chain of at least 12 carbonatoms.